Automatic telephone system



A. J. RAY

AUTOMATIC TELEPHONE SYSTEM Patented Get. 23, 1928.

tJNlTED STATES PATENT OFFICE.

ARTHUR J. BAY, OF CUBA, ILLINOIS, ASSIGNOR, BY ME NE ASSIGNMENTS, TO AUTO- IVIATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed May 22, 1325, Serial No. 31 987.

p This invention relates to automatic telephone systems in general, but is more particularly concerned with the methods of establishing toll or long distance connections to subscribers in an automatic party-line telephone s atom; and the object, broadly stated, is the provision of a new and improved auton; atic party-line toll connector. 7

An incoming toll call from a distant station is extended by a toll operator at a local automatic exchange through the medium of automatic toll switches responsive to impulses dialled by means of a calling device by the toll operator. To signal a certain subscriber of a party line, a digit in addition to the number of the called line is dialled to select the proper frequency of ringing current to which the bells of only that certain subscriber respond. For various reasons. 1t is desirable that the digit that selects the ringing current and distinguishes each subscriber of a party line be the last digitdialled. Particularly is this necessary to maintain a uniform numbering system in a multi-office area consisting of both manual and automatic exchanges in which the manual practice has been to distinguish the individual subscribers of a party line by a digit or letter at the end of the line number. Having the last digit select the subscriber of a party line also simplifies the numbering scheme and the records of the interconnections Within the exchange and also facilitates the tracing of calls in the exchange.

It is also imperative that the time required to complete the connection for a long distance call be as short as possible. To facilitate the reducing of this time to a minimum, it is desirable, if a'substation tests busy when the toll operator first attempts to complete a connection, that the toll operator be able to camp on the busy called line and that she be given a signal soon as the line becomes idle.

In the ordinary connector circuits of the camp-on-busy type as are well known in the art, the caller subscribers line is tested for thebusy or idle condition and the impulsing circuit opened as soon as the two line selecting digits have been dialled. A frequency selecting mechanism added to the ordinary connector of this type operable by a digit dialled after the two line selecting digits would not be a desirable combination. The toll operator, after dialling the two line selecting digits and finding the line busy,

Renewed August 29, 1927.

would be required to wait until after the called line became idle before the frequency selecting digit could be dialled. This condition would invite error in that the operator might neglect to dial the digit to select the frequency of ringing current, or the operator might forget the number to dial by the time the called line became idle.

Heretofore this objectionable feature has been overcome by arranging the frequency selecting mechanism to be operated b the digit preceding the two line selecting c igits. However, such an arrangement does not have the desirability of frequency selection last as pointed out in a previous paragraph. In the present invention a connector switch of the camp-on-busy type has been provided that permits the frequency to be selectedbythe last digit'and that eliminates the disadvantages that have heretofore been inherent in such an arrangement, the method employed being the provision of means for delaying the testing of the called line until the frequency selecting digit has been dialled.

Therefore, it is the principal object of this invention to provide a connector switch that permits the frequency to be selected on the last digit dialled, that make it possible to camp on a busy line and give signal when this line becomes idle, and that delays the testing of the called line for the busy or idle condition until the digit selecting the he quency has been dialled. In this switch. when the line is found busy, the frequency will already have been selected, and the only further operation required when the line becomes idle is for the switch, under the control of the operator, to automatically connect the selected ringing current to the called line.

The means by which the foregoing objects, together with others not specifically mentioned, are accomplished will be fully set forth hereinafter, reference being had to the accompanying drawing in which is shown the apparatus with which this invention deals and also sufiicient other apparatus to enable the invention to be clearly explained and understood and its utility appreciated.

1511 incoming toll call is extended by the toll operator at a local automatic exchange by means of a cord, a calling jack and its associated trunk circuit, one or more selectors, depending on the size of the local system. a toll transmission selector, and a toll connector, to the called substation. The one or more selectors and the toll transmission selector may be mechanically of the well known vertical and rotary type, each responsive to a digit dialled by the operator, functioning to select a trunk to an idle succeeding switch of a group of such switches. The toll trans-- mission selector selects an idle toll connector of the group in whose banks the line of the called substation terminates. For a description of the apparatus at the toll operators switchboard, and the toll transmission selector circuit, reference may be made to the copendine; application of John icks, Serial No. 482,765, filed July 5, 1921. The other selector, or selectors, may be of the usual. twowire type in common use.

. Referring to the accompanying drawing, the reference character C indicates the improved toll connector, shown by means of the usual circuit diagram. ldechanically, this svitch may also be of the well known vertical and rotary type.

Associated with the connector C, and individual to it, is the frequency selecting mech anism ES. Responsive to the lirst two of the last three digits dialled, the connector selects the called line. In response to the last digit, the frequency selecting mechanism FS is operated to select the frequency of the ringing current.

The reference character LS in icates the line switch individual to the party line comprising conductors 120 and 121. The line switch is of the rotary type in which the wipers have no normal position and move in a forward direction only. The individual substations of the party line are indicated by the reference characters A to A only the bells of the substations A. to A being shown.

Having explained the purpose of the invention and the apparatus involved, the operation of the equipment may now be ex plained more in detail. For this purpose it will be assumed that the long; distance op erator at the local automatic exchange has received the information that a long distant connection is desired with the party line suhstation A.. It will also be assumed that the local system is a 10,000 line system. it will, therefore, require four digits to select a line, and an additional digit to select the frequency of ringing current when calling a substation on a party line. The local toll operator completes the desired connection in the usual manner by inserting the calling plug of a cord into the jack of a. trunlr extending to an idle first selector, and dialling the directory number of the substation r.

In response to the first digit dialled, the first selector raises its wipers opposite the level of bank cont-acts at which access is had to the proper group of toll transmission selectors and rotates them to select a trunk to an idle toll transmission selector in that group. In response to the second digit dialled, the toll transmission selector raises its wipers opposite the level of bank cont acts having access to the group of connectors in whose banks the line to the substation A terminates, and then rotates its wipers to select a. trunk to an idle one of these connectors. lt will he assumed that the trunk selected is the trunk to connector C, comprising conductors 717 l-, inclusive, accessible at the toll transmission selector bank contacts 7 5-7 8, in elusive.

The two line conductors are thereby extended by way of bank contacts and 78, conductors 71 and 7 l, normally closed springs controlled by armatures 37 and 4:2, armatures 4.8 and 4:7 and their resting contacts, the upper and lower windings of the line relay 2 of the connector C to battery and ground, respectively. Line relay 2 energizes and opens a point in the circuit of the switching relay 9. to be described later, at armature 20, and closes a circuit for the release relay 3 from ound by way of the resting contact of armature 4:6 and said armature, armature 21 and its workingcontact, winding of release rela" o to battery. Release relay 0 operates and epares a circuit for the ringcut-off relay 7 at armature 22, prepares a circuit for the cut-in relay 8 at armature 23, and prepares a circuit for vertical magnet 11 at armature 24:.

In response to the third digit dialled, the circuit of the line relay 2 is opened a corresponding number of times. When relay 2 falls back the first time, a circuit for. the first impulse is closed from ground by way of resting contact of armature l6 and said armatiu'e, armature 21 and its resting contact, armature 2a its working contact, oli' normal springs 52 and 51, winding of the series relay 4, winding of the vertical magnet ll. to battery. Series relay 4 operates and prepares a circuit for the remaining impulses at armature 25 and its working contact. Upon the first vertical step of the switch, the oll normal springs are shifted so that the ren'iaining impulses to the vertical magnet traverse a new circuit which is the same the one traced above except that it includes elf normal springs 52 and 53,'arniature 25 and its working contact. Vertical magnet 11 operates to raise the switch wipers 80, 81, and 82 step by step until they are opposite the level of bank contacts on which the'linc extending to the substation A tern'iinatcs. The slow-to-release series relay 4 maintains its armature attracted throughout the vertical movement of the switch. At the termination of the vertical movement, the series relay 4t deenergizes, transferring the impulsing circuit to the rotary magnet 12.

In response to the fourth digit dialled, a series of interruptions is again produced in the circuit of the line relay 2. At each retraction of the armature 21, an impulse of Inc current is sent to the rotary magnetl2 over a circuit extendin from ground by way of the resting contact of armature 46 and said armature, armature 21 and its resting contact, armature 2a and its working contact, springs 52 and 53, armature 25 and its resting contact, resting Contact of armature 27 and said armature, through the winding of the series relay 6, armature 10 and its resting contact, armature 3 1 and its resting contact, through the winding of the rotary magnet 12 to battery. T he rotary inagi'iet 12 operates and rotates the switch wipers 80, 81 and 82 into engagement with the set of bank contacts as sociated with the line to substation A these being bank contacts 83, 8%, and 85. The cam 66 rotates with the switch shaft and upon tne first rotary step allows the springs 54: to make contact. The slow-to-release series relay 6 energizes in series with the rotary magnet and maintains its armature attracted throughout the rotary movement. In operating, relay 6 holds the circuit of the. ring cut-ofi' relay open at armature The actuation of armatures 31 and 32 perform no useful function at this time.

At the end'of the rotary movement of the switch wipers, the relay 6 deenergizes and thereby closes the circuit for the ring cutoff relay 7 at armature 30, which may be traced from ground by way of the working contact of armature 22 and said armature, resting contact of armature 4-5 and said armature, cam springs 54, resting contact of armature and said armature, through ,the upper winding of the ring cut-off relay 7 to battery. Ring cut-oif relay 7 operates and closes a holding circuit for itself at armature and its working contact, ground being furnished to the holding conductor 7 3 by the toll transmission selector switch preceding the toll connector. In operating, ring cut-off relay 7 transfers the impulsing circuit from the rotary magnet 12 to the stepping magnet 13 of the frequency selecting mechanism at armature 34, and disconnects the ringing circuit from conductors 90 and 91 at arinatures 33 and 36, respectively.

The toll operator now operates her calling device in accordance with the final digit of the number, which is the digit that selects the proper frequency of ringing current to signal the substation A For convenience, the substations A. to A inclusive, have been numbered in accordance with the digits to which they respond. Therefore, the final digit to be dialled to signal the substation A is the digit 0. When the calling device is operated for his digit, the line relay 2 transmits ten impulses to the stepping magnet 13 of the frequency selecting mechanism FS orer a circuit which may be traced from groundby way of the resting contact of armature 46 and said armature, armature 21 and its resting contact, armature 24; audits working contact, off normal springs 52 and 53, armature 25 and itsresting contact, rest-' ing contact of armature 27 and said armature, winding of series'relay 6, armature 40 and its resting contact, armature 34 and its working contact, winding of stepping magnet 13 to battery The slow-to-rclease series relay 6 is energized in series with the stepping magnet and 'maintains its armature attracted throughout the frequency selecting movement. In operating, relay 6 closes a shunt around armature 2. at armature 31 prepares the testing'circuit for the busy relay 5 at armature 32 and its Working contact. By the operation of the stepping magnet 13, the wipers 59 and 57 are rotated step by step and are finally brought to rest in engagement with the tenth contacts of their respective banks. On the first movement of the wipers 59 and 5'7, off normal springs and 56ers closed, thereby closing the testing circuit and preparing the circuit of the rclease magnet 1a. g If the line to substation A is idle, the cutin relay 8 will energize immediately following the release of the series relay 6, and the succeeding operations take place as will be described. hereinafter.

It will be assumed, however, that the line to substation A is busy at this particular time Under this condition, there will be ground potential on the test contact 84:, supplied to it either by another connector whose wipers are in engagement with contacts similar to bank contacts 83, 84, and 85, and multiplied with them, or by the armature 105 in an operated position to which ground is supplied from a succeeding switch, as is well known in the art. When the off normal springs of the frequency selector FS are closed, a circuit is completed from ground on the test contact 84;, test Wiper 81, off normal springs 55, armature 32 and its working contact, winding of the busy relay 5 to battery. Busy relay 5 operates and prepares a holding circuit for itself at armature 28-; opens the original impulsing circuit at armature 27; and opens a point in the circuit of the cut-in relay 8 at armature 26. Asa further result of the operation of the busy relay 5, the busy tone from the busy machine B is put on the conductor 74 at armature 29 and its working contact. At the termination of the impulses for the stepping movement, series relay 6 deenergizes and opens the initial impulsing circuit at'armature 31, and opens the initial test circuit and closes a point in the circuit of the cut-in relay 8 at armature 32, also closing the locking circuit for busy relay 5 at the normally closed springs controlled by armature 32. Since the impulsing circuit is now opened at both armatures 27v and 31, the switch wipers can not be rotated off the busy contacts by any accidental manipulation of the dial.

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The busy tone is reproduced in the operators receiver, thereby notifying her that the desired line is busy. The supervisory lamp in the operators cord will also remain extinguished. Leaving the connection set up, the operator may restore her listening key and perform other duties, as may be required.

l/Vhen the line to substation A becomes idle, ground will be removed from the test contact 84. The removal of ground from the test contact 84 causes the busy relay 5 to fall back and openits locking circuit at armature 28 and close the circuit for the cut-in relay 8 at armature 26, which may be traced from ground at the workin g contact of armature 23 and said armature, the resting contact of armature 26 and said armature. through the lower winging of the cut-in relay 8, resting contact of armature 32 and said armature, off normal springs 55, test wiper 81, test con- .tact 84, winding of the switching relay 101 of the line switch LS, resting contact of armature 108 and said armature, winding of the stepping magnet 103 to battery. On account of the interlocking arrangement between the armatures of switching relay 101 and the line relay 102 of the line switch LS, the switching relay 101 is allowed to operate only sufiiciently to disconnect the line conductors 120 and 121 from the line switch LS. The cut-in re-' lay 8 operates and closes a locking circuit for its upper winding at armature 39, ground being supplied to conductor 72 from the preceding switch, opens a point in the lmpulsing circuit at armature 40, prepares a circuit for the switching relay 9 at armature 38, places a ground on the test wiper 81 at armature 41 to make the line of substation A test busy to any. other incoming call, and reverses the battery potential supplied to conductors 71 and 74 through the line relay 2, at armatures 37 and 42. Reversing the battery potential to conductors 71 and 74 causes a reversal of current in one of the windings of the electropolarized relay in the toll transmission selector circuit (not shown). This electro-polarized relay operates and closes a locking circuit for itself, causes the lighting of the supervisory lamp in the operators cord, and con.- nects a battery supply to conductors 71 and 74 which directly opposes the battery as supplied through the line relay 2 of the conductor Q. Line relay 2 is caused to deenergiz'e and close a circuit for the switching relay 9 at armature 20. Switching relay 9 operates and disconnects the upper and lower windings of the line relay 2 from the conductors 71 and 74 and connects these conductors to the wipers 82 and 80, at armatures 47 and 43, respectively, thereby completing the connection to the line of substation A. In operating, switching relay 9 also prepares a circuit for the ring-back tone at armature 44, opens another point in the initial energizing circuit of the ring cut-off relay 7 at armature 45, and disconnects ground from armature 46 before the circuit of release relay 3 is opened at armature 21 which allows armature 24 to drop back. The circuits for the release magnet 10 and the release magnet 14 are thus held open at armature 46.

The lighting of the supervisory lamp at the operators position gives the local toll operator signal that connection with the substation A has been obtained. She may now signal the subscriber at the substation A and after the subscriber answers, notify him that a long distance call is being extended to him. To signal the subscriber at substation A, the local long distant operator mo1nentarily actuates the ringing key of her cord circuit. This causes a relay in the previously mentioned toll transmission selector circuit to deenergize for an instant and remove the ground potential from conductor 73. Removing ground from conductor 7 3 allows the ring cut-off relay 7 to fall back and open its holding circuit at armature 8-5, and'complete the circuit for ringing current at armatures 33 and 36. The release of relay 7 also closes the circuit for the ring-back tone at the normally closed springs controlled by armature S3. The ring-back tone current, also furnished by generator R, is thus supplied to conductor 74. As is evident from the drawing, regardless of the generator selected for ringing, the ring-back tone current is always supplied by generator R. The tone reproduced in the local toll operators receiver signifies that the called subscriber is being signalled. Since the wipers 59 and 57 are now in engagement with the contacts 60 and 58, respectively, the ringing circuit may be traced from the grounded generator 1%, through the contacts of the ringing interrupter, conductor 65, bank contact 58, wiper 57 resting contact of armature 36 and said armature, armature 42 and its working contact, armature 47 and its working contact, switch wiper 82, bank contact 85, conductor 121, the normally closed switchhook contacts at substation A and the ringer at the said substation to ground. The above circuit is intermittently opened and closed by the operation of the ringing interrupter, and the ringer at substation A is operated at intervals to signal the called subscriber. It is understood, of course, that the ringing current also flows through the ringers of substations A to A inclusive, at the same time, but the ringers at these other substations are tuned so that they will not respond to ringing current of the frequency now being used. This is according to' the well known practice of harmonic signalling, in which only one subscriber of a party line is signalled at one time.

When the called subscriber at substation A removes his receiver to answer the call,

the ringer at substation A is disconnected l and a direct current circuitis completed extending from the superimposed battery at the ringing generator R to conductor 121, as previously traced, through the substation A to conductor 120, bank contact 83, switch wiper 80, working contact of armature 43 and said armature, working contact of armature 37 and said armature, armature 83 and its resting contact, wiper 59, bank contact 60, through the lower winding of the ring outoff relay 7 to ground. The ring cut-oft relay 7 will again energize and closethe locking cir-' cuit for its upper winding at armature 85, and complete the talking connection at armatures 33 and 36. The local toll operator may now converse with the subscriber at substation A and inform the subscriber that a long distance connection with him is being eX- tended.

If the extension of this long distance call does not include many intermediate toll ofiices, or comes from a relatively short distance so that the calling party can quickly be called to his telephone, the subscriber at substation A is instructed to hold his receiver and wait for the calling party to begin conversation. It is assumed, however, that it may take some time before the distant calling party can be summoned to the phone,-in which case the subscriber at substation A may replace his receiver but is requested to be in readiness to immediately answer the call when he is again signalled.

The local toll operator now notifies the distant toll operator that connection has been completed with the local called subscriber. lVhen the local toll operator is notified that the distant calling subscriber has been summoned to the phone, the local toll operator will again signal the subscriber at substation A by momentarily operating the signalling key in her cord circuit. The ring cut-off relay 7 will again operate as described before and cause the ringing current to be supplied to the line conductors 120 and 121. When the subscriber at substation A removes his receiver, the energizing circuit for the ring cut-off relay 7 is again closed, and relay 7 operates to complete the talking connection. The subscriber at the distant calling substation may now converse with the subscriber at substation A.

Removing the receiver at substation A also places a bridge across the conductors 71 and 74, which closes a circuit for the battery feed relay in the toll transmission selector circuit. This battery feed relay operates to extinguish the supervisory lampin the toll operators cord circuit, thus giving the toll operator the usual supervision.

When the conversation has terminated, the two subscribers will replace their receivers on their respective switchhooks. The replacing of the receiver at substation A opens the bridge across'the conductors 71 and 74, thereby opening the circuit for the previously mentioned battery feed relay in the toll transmission circuit. This battery feed relay then deenergizes and again closes a circuitfor the supervisory lamp in the toll operators cord circuit. The lighting of this supervisory lamp signals the local toll operator that the called subscriber has rcplaced his receiver. The local toll operator will also receive the usual disconnect signal from the originating distant toll operator. Upon receiving these signals, the local toll operator will proceed to pull down the connection. by removing the calling and answering plugs from their respective jacks asso ciated therewith. Ren'ioving the calling plug from the jack will release the selectors and the toll transmission selector in the usual manner. V hen the toll transmission selector is released, ground is removed from the hold ing conductor 72 and from the ringing conductor73. Removing ground from conductor 73 opens the holding circuit for relay 7; removing the ground from the conductor 72 opens holding circuits for relays S and 9. Relays 7, 8, audit) are thus deenergized and fall back to normal. The circuits for the release magnet 10 and for the release magnet14 are closed at armature 46. The release magnets operate to restore the connector switch to its normal position. The holding ground for the switching relay 101 of the line switch LS is removed at armature 41, and the relay 101 is deenergized.

A brief explanation will now be given of the manner in which the other substations of the line may be signalled. Each of the substations A, A A and A may be signalled independently by dialling the digits 6, 7, 8, and 9, respectively, as the final digit, and the operations are exactly the same as when substation A is called, except that a different frequency of ringing current is selected. It is understood in this connection that the con ductors 61 to 64, inclusive, all extend to sepa rate ringing current generators similar to generator R and that these generators are all of different frequencies. The ringers at the five substations just referred to are all connected from the line conductor 121 to ground. In order to operate the ringers at the remaining substations A to A inclusive, which are connected from theline conductor 120 to ground, digits 1, 2, 3, 4, and 5, respectively, must be dialled as the final digits. Suppose for example that it is desired to call the substation A The ringer at this substation is tuned to the same frequency as the ringer at substation A. The

final digit to be called in this case is the digit 5, in repsonse to which the wipers of the frequency selecting mechanism F S are advanced five steps into engagement with the fifth contacts in their respective banks. When the wiper 59 comes to rest on the fifth contact, the ringing generator R shown on the drawings is again selected, as the first five contacts in the bank associated with the wiper 59 are connected in multiple with the last five contacts in the bank associated with the wiper 57. When ground is removed from the conductor 73 as a result of the actuation of the ringing key by the local toll operator, the ring cut-ofi relay 7 is deencrgized, thereby completing the ringing circuit substantially the same as previously described, except that in the present case, the ringing current is applied to line conductor 120 by way of conductor 65, bank contact 67, and wiper 59, instead of conductor 121 by way of bank contacts 58 and switch wiper 57. The ringing current is then supplied over conductor 120 to the ringers of the substations A to A, inclusive, to ground. The ringer at substation A is accordingly operated. Substations A to A inclusive, may be called in the same manner by dialling, as the final digit, the digits which correspond to these substations.

Having described this invention, what is considered new and is desired to have protected by Letters Patent will be pointed out in the appended claims.

WVhat is claimed is:

1. In a telephone system, an automatic line selecting switch, an automatic ringing current selecting switch individual to said first switch, means for first operating said first switch to select a line and for then operating said second switch to select ringingcurrent, means effective only after said second switch has been operated for testing said line, means for preventing the completion of the connection it the line is busy, and means for automatically completing the connection when the line becomes idle.

2. In a telephone system, an automatic line selecting switch, an automatic ringing-current selecting switch individual to said first switch, means for first operating said first switch to select a line and for then operating said second switch to select ringing-current, means for testing the line, means for delaying the testing of the line until said second switch has been operated, means for preventing the completion of the connection it the line is busy, and means for automatically completing the connection when the line hecomes idle.

3. In a telephone. system, an automatic line selecting switch, an automatic ringingcurrent selecting switch individual to said first switch, means for first operating said first switch to select a line and for then operating said second switch to select ringingcurrent, means for testing said line for the busy or idle condition, means for maintaining said last means disabled until said second switch has been operated, means for preventing the completion of the connection it the line is busy, and means for automatically completing the connection when the line becomes idle.

4. In a switching device for extending connections to party lines, means for selecting a line and for thereafter selecting the desired party on the selected line, a relay for complet ing connection to the selected line, a circuit for said relay adapted to be completed only after the party selection is accomplished, means for preventing the closure of said circuit if the selected line is busy, and means for completing said circuit consequent to the selected line becoming idle.

5. In a switching device for extending connections to party lines operable in accordance with the last three digits in a telephone number, means for selecting the line responsive to the first two digits received, means for selecting the party responsive to the last digit, means for testing the line, means for delaying the testing operation pending the receipt of the last digit, means for preventing the completion of the connection it the selected line is busy, andmeans for automatically completing the connection'when the selected line becomes idle.

6. In a line and ringing current selecting switch, a line relay, a stepping magnet controlled by said line relay for causing the switch to select a line, a ring cut-ofi" relay, means for energizing said ring cut-ofi relay responsive to completion of the line selection, a stepping magnet for causing ringing current selection, and contacts on said ring outoff relay forshitting the control exercised by the line relay from the firststepping magnet to the second. I 1

7. In. a. toll connector comprising a line selecting switch and a ringing current selectbe energized automatically during'the process of line selection to prevent immediate ringing of the selected line, a line selecting magnetand a ringing current selectingmagnet, a line relay controlling both said magnets, contacts for causing said line relay to control the line selectinginagnet first and the other magnet last, and means for causing the energization of the ring cut-oil relay to take place at the time the control exercised bythe. line relay is to be shifted from one magnet to the other so that said contacts may be controlled by said ring'cut-ofi' relay. 7

8. In a telephone system, a toll connector switch, a ringing-current selecting switch, means for first operating said connector switch to select a line and for then operating said ringing-current selecting switch to select ringingcurrent, and means efi'ective as soon as said ringing-current selecting's'witch has been moved ofi normal for testing said line.

9. In atelephone system, a toll connector switch, a ringing-current selecting switch, means for first operating said connector mg switch, a ring cut-off relay adapted to switch to select a line andfor then operating said ringing-current selecting switch to select ringing-current, means for testing the line, and means for delaying the testing of the line until the operation of said ringing-current selecting switch has been started.

10. In a telephone system, a toll connector switch, a ringing-current selecting switch, means for first operating said connector switch to select a line and for then operating said ringing-current selecting switch to select ringing-current, a circuit for testing the called line, and means including off-normal springs on said ringing current selecting switch for maitaining said testing circuit open until the said ringing current selecting switch has operated.

11. In a switching device for extending connections to party lines, means for selecting a line and for thereafter selecting the desired party on the line, a relay for testing the line, a circuit for said relay, and means for completing said circuit as soon as the party selecting operation is started.

12. In a switching device for extending connections to party lines operable in accordance with the last three digits in a telephone number, means for selecting the line responsive to the first two digits received, means for selecting the party responsive to the last digit received, means for testing the line, and means for delaying the testing operation pending the receipt of the last digit.

In witness whereof, I hereunto subscribe my name this seventh day of May, A. D. 1925.

ARTHUR J. RAY. 

